Comparative Biodistribution and Radiation Dosimetry of 68Ga-DOTATOC and 68Ga-DOTATATE in Patients with Neuroendocrine Tumors

Ga-68-DOTATOC and Ga-68-DOTATATE are 2 radiolabeled somatostatin analogs for in vivo diagnosis of neuroendocrine tumors with PET. The aim of the present work was to measure their comparative biodistribution and radiation dosimetry. Methods: Ten patients diagnosed with neuroendocrine tumors were included. Each patient underwent a 45-min dynamic and 3 whole-body PET/CT scans at 1, 2, and 3 h after injection of each tracer on consecutive days. Absorbed doses were calculated using OLINDA/EXM 1.1. Results: Data from 9 patients could be included in the analysis. Of the major organs, the highest uptake at 1, 2, and 3 h after injection was observed in the spleen, followed by kidneys and liver. For both tracers, the highest absorbed organ doses were seen in the spleen and urinary bladder wall, followed by kidney, adrenals, and liver. The absorbed doses to the liver and gallbladder wall were slightly but significantly higher for Ga-68-DOTATATE. The total effective dose was 0.021 +/- 0.003 mSv/MBq for both tracers. Conclusion: The effective dose for a typical 100-MBq administration of Ga-68-DOTATATE and Ga-68-DOTATOC is 2.1 mSv for both tracers. Therefore, from a radiation dosimetry point of view, there is no preference for either tracer for PET/CT evaluation of somatostatin receptor-expressing tumors.